Push-pull amplifier system



Feb, 6, 1934. B.y F. MlEssNER v 1,945,092,

PUSH-PULL AMPLIFIER. SYSTEM Filed Nov. 8, 1929 MHT/V555 @My/MM@ @51g @www m T45 filaments of tubes VT1 and VTz.

Patented Feb. 6, 1934 UNITED STATES PATENT OFFICE PUSH-PULL Murrina SYSTEM ration of Delaware Application November 8, 1929. Serial No. 405,584

10 Claims.

My invention relates generally to push-pull amplier systems and more particularlyA to means within said system for maintaining a balance between the tubes thereof. The primary object of my invention is to maintain a perfect balance between the tubes of a push-pull amplier system so that the impedances of the tubes are identical with the lresultant equalization of amplification and like elects.

Further objects will become apparent as the description of my invention is developed by reference to the accompanying drawing forming a part of this specification in which Fig. 1 diagrammatically represents one form of push-pull amplifier system in which my invention has been incorporated, and

Fig. -2 diagrammatically illustrates a modication thereof.

Referring to the drawings VT1 and VTz designate two electron tubes, the grids of which are connected to the split secondary S1 of pushpull input transformer IT, the center tapof which is connected to the negative terminal of a source of fluctuating current SF. The plates of the tubes vVTi and VT2 are connected to the primary P of the output transformer OT in the usual manner, the midpoint of the primary P being connected to the positive terminal of a source of fluctuating current SF.

In Fig. 1 I have shown the filaments of tubes VT1 and VT2 energized from a common source of alternating current through a heating transformer I-IT, the center tap CT of which is connected through a grid biasing resistance BR to the negative terminal of the source SF. Between one leg of each filament and .one terminal of the heating transformer I-lT, I have provided a potentiometer P1 the resistance R1 of which is connected between the respective filaments Of VT1 and VTz.

In Fig. 2 I have provided two potentiometers P1 and Pz, the resistances R1 vand R2 of which are in series in the common connections for the In this instance I have also provided a center tap potentiometer CP, the variable .tap of which is .connected to the bias resistance BR in lieu of center tap connection CT of Fig. 1.

In the operation of Fig. 1, the filament emission and therefore the impedance of the tubes VT1 and VTz may be differentially controlled by varying the movable tap of potentiometer P1 so that the amplification of each tube may be made to .equal that of the other. In. this Cil system, with tubes widely variant in amplication characteristics, however, there Amaybe' a slight displacement of the center tap connection CT with respect to the electrical'center oi' the Vfilaments of tubes VTi and VTz. Q0 objection I have eliminated in the connection shown in Fig. 2. In the structure of this liigure, variable taps of potentiometers P1 and P2 may be varied in a manner similar to that of the one potentiometer P1 of Fig., l. vIf these Apo- Q5 tentiometers are varied equally as by anni control of the two movable elements, thereswill b e no displacement of the center tap for the filament system. However, if it is not vdesirerl'to have uni-control of potentiometers P1 and Pz 7,0 the `electrical center of each of the laments may be obtained by varying the'movable `tap of the Acenter tappotentiometer CP. Itis to be understood that the center tap potentiometer CP may also be used in lieu ofthecentertap 15 n Vconnection CT of Fig. 1 vwithout departing from the spirit of my invention.

While I have described my invention as embodied in certain specific circuits, it is to be understood that various modifications Athereof $0 will be apparent to those skilled in the art without 'departing from the spirit of my invention4 as'defined by the scope of the claimsiappended hereto.

Having thus described my mventionwhatl claim is:

1. In an amplier system, the combination of Aa pair of electron tubes,pushpull input and output circuits therefor, a resistance common to said input and output circuits for determining the biasing of said tubes, said tubes having a common `ilament energizing system connected to a source of alternating current, the filaments of said tubes being connected in parallel in'said system, and a potentiometer, the resistance of which is series connected between corresponding legs of the lfila ment of each tube and the variable tap of 4which is connected to one terminal of said energizing system, the other terminal of said energizing system being connected to the other corresponding legs of the filament of each tube, whereby the im- A pedance of said tubes may be differentially Varied.

2. In an amplier system, the combinationof a pair of electr-on tubes, push-pull input and output circuits therefor, said tubeshaving a'common lament energizing system connected toa source of alternating current, the filaments of said tubes being connected in parallel'in said system, and a plurality of potentiometers the' resistances of which are series'connected between corresponding legs of said filament and the variable taps of which are connected to the terminals of said energizing system, whereby the impedances of said tubes may be differentially varied.

3. In an amplifier system, the combination of a pair of electron tubes, push-pull input and output circuits therefor, said tubes having a common filament energizing system connected to a source of alternating current, the filaments of said tubes being connected in parallel in said system, a plurality of potentiometers the resistances of which are series connected between corresponding legs of said filament and the variable taps of which are connected to said energizing system, whereby the impedances of said tubes may be differentially varied, and a common means for obtaining tlie electrical center of both of said iilaments.y

4. In an amplifier system, the combination of a pair of electron tubes, push-pull input and output circuits therefor, said tubes having a common lament energizing system connected to a source of alternating current, the filaments of said tubes being connected in parallel in said system, a plurality of potentiometers the resistances of which are series connected between corresponding legs of said filament and the variable taps of whichv are connected to said energizing system, whereby the impedances of said tubes may be differentially varied, and a common grid return connection from the center of said push-pull input circuit to the electrical center of both of said filaments.

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A5. In an amplifier system, the combination of a pair of electron tubes, push-pull input and output circuits therefor, said tubes having a common filament energizing system connected to a source of alternating current, the laments of said tubes being connected in parallel in said system, a plurality of potentiometers the resistances of which are series connected between corresponding legs of said lament and the variable taps of which are connected to said energizing systeni, whereby the impedances of said tubes may be diiferentially Varied, and a common grid return connection from the center of said push-pull input circuit to the electrical center of both of said nlaments, said connection including a potential developing element for determining the grid bias of said tubes.

6. In an amplifier system, the combination of a pair of electron tubes, push-pull input and output circuits therefor, said tubes having a common lament energizing system connected to a source of alternating current, the filaments of said tubes being connected in parallel, a plurality of potentiometers the resistances of which are series connected between corresponding legs of said filament and the variable taps of which are connected to said energizing system, whereby the impedances of said tubes may be differentially varied, and a common grid return connection from thecenter of said push-pull input circuit to the electrical center of both of said filaments, said connection including a resistance whereby the combined plate current -of said tubes determines the grid bias for each of said tubes.

'7. In an amplifier system, the combination of a pair of electron tubes, push-pull input and output circuits therefor, said tubes having a common lament energizing system connected to Va source of alternating current, the filaments of said tubes being connected in parallel in said system, and a plurality of potentiometers the resistances of which are series connected between corresponding legs of said filaments and the variable taps of which are connected to said energizing system, whereby the impedance of said tubes may be differentially varied, a resistance shunted across the terminals of said energizing system and a connection including a resistance between an intermediate point of said shunted resistance and a point in said input circuit.

8. In an amplier system, a pair of electron discharge devices arranged in push-pull relationship comprising an input circuit including the secondary winding of a transformer, and an output circuit including the primary winding of a transformer, said discharge devices having a common lament energizing system connected to a source of current, the laments of said devices being connected in parallel in said system, and a pair of resistances in series each thereof connected respectively between `the corresponding legs of said laments, a variable connection between a point on one of said resistances and a terminal of said filament energizing system and a connection between a point on Vthe other of said resistances and the other terminal of said filament energizing system, a resistance shunted across the two terminals of said lament energizing system, a connection including a resistance between a point on said shunting resistance and a point on said secondary winding and a connection including a source of energy, between the secondary winding end of said last named resistance and a point on said primary winding. 1

9. In an amplifier system a pair of electron* discharge devices arranged infpush-pull relationship including an input circuit having the secondary winding of a transformer, and an output having the primary winding of a transformer, said discharge devices having acommon filament energizing system connected to a source of energizing current, the filaments of said devices being connected in parallel in said lastnamed system, a resistance in series between corresponding legs of the filament of each discharge device, a variable connection between a point on said resistance and a terminal of said filament energizing system and a connection between the other terminal of said lament energizing system and a point common to the other corresponding legs of said filaments, a resistance shunted across the two terminals 'iis of said nlament energizing system, a connection on said shunting resistance and a po-int on said secondary winding and a connection including a source of energy between the secondary winding end of said biasing resistance and a point on said primary winding.

10. In an amplifier system the combinationv of a pair of electron tubes, push-pull input and output circuits therefor, said tubes having a common nlament energizing system connected to a source of alternating current, the filaments of said tubesbeing connected in parallel in said system, a resistance in series between corresponding legs of the filament of each tube, a Variable connection between a point on saldresistance and a terminal of said lament energizing system and a connection between the other terminal of said filament energizing system and a point common to the other corresponding legs of said filaments, an impedance elfectively connectedy across said source of altering a source of uni-directional fluctuating plate current and said potential developing element in series, and means for variably disposing said common connection to said impedance to allow for adjusting said common connection to a point of said impedance to produce equalized effects in the outputs of both tubes.

BENJAMIN F. MIESSNER. 

